Fix hot-path raising in ActionDispatch::Static

Using File.stat where a file does not exist raises an exception.

Since ActionDispatch::Static does this:

def call(env)
  @file_handler.attempt(env) || @app.call(env)
end

... this means that around 8 exceptions are raised and rescued on each
request which is passed to the application.

This change improves latency by ~.14 milliseconds on all applications.

Partial revert of rails#37265

Author: nateberkopec

actionpack/lib/action_dispatch/middleware/static.rb

@@ -137,11 +137,8 @@ def try_precompressed_files(filepath, headers, accept_encoding:)
       end
 
       def file_readable?(path)
-        file_stat = File.stat(File.join(@root, path.b))
-      rescue SystemCallError
-        false
-      else
-        file_stat.file? && file_stat.readable?
+        file_path = File.join(@root, path.b)
+        File.file?(file_path) && File.readable?(file_path)
       end
 
       def compressible?(content_type)